Seattle developer Wright Runstad said it plans to start work Monday on the Spring District, a 36-acre, mixed-use project in Bellevue.

Demolition of a warehouse and installation of streets and utilities will position the developer for groundbreaking on a 491,000-square-foot office complex in early 2014 if an anchor tenant signs on or the market is strong enough to justify speculative construction, said Greg Johnson, president of Wright Runstad.

Seattle-based Security Properties plans to start building a 316-unit apartment complex in the Spring District next year as well.